Composites of fiber-reinforced rubber are useful for many purposes including articles of manufacture such as tires and industrial products which contain at least one component comprised of a composite of fiber-reinforced rubber. Typically such fibers are in a form of a cord comprised of cabled, or twisted, yarns. Such fibers can be of various materials including, for example, nylon, aramid, polyester, carbon, polyvinyl alcohol, steel wire including brass coated steel wire, rayon, cotton and glass.
An important requirement of such reinforced rubber composites is the adhesion of the reinforcing fiber, or cord thereof, to the rubber itself. Such adhesion is of particular importance where the resulting rubber composite is intended to be subjected to considerable flexing and distortion, such as for example may be experienced in a typical operation and use of tires, particularly pneumatic tires, and industrial power transmission and conveying rubber belts.
The invention relates to treating yarn, which may be in a form of a cord comprised of a plurality yarns, to rubber compositions which contain such treated yarn and to articles of manufacture, including tires, which contain at least one component comprised of such rubber composition.
Various methods have been historically used to obtain adhesion of fiber and cords thereof to rubber compositions which involve pre-treating the cord with an adhesive.
For example, the cord has been pretreated prior to adhering to rubber by dipping, followed by drying, in an aqueous emulsion (dispersion) comprised of a rubber latex which contains a resorcinol/formaldehyde resin (RFL) which is a treatment well known to those having skill in such art. Such rubber for said latex is typically a butadiene/styrene/vinylpyridine terpolymer. The resorcinol/formaldehyde resin is understood to be a primary element of the adhesive between the cord and the rubber with the latex being useful in reducing the modulus of the resin. Other advantages and features of the RFL for adhering cord to rubber are generally well known to those having skill in such art.
Sometimes, particularly for polyester cords, a single dip or a double dip adhesive system might be used to coat the cord with an adhesive layer.
In the double dip system, cord (e.g. cord of a plurality of twisted polyester yarns) is treated with a first dip such as a dispersion of a phenol-blocked diisocyanate, particularly a phenol-blocked diphenylmethane diisocyanate, an epoxy resin, wetting agents and water. The treated cord is cured (e.g. the coating on the cord is cured), then treated with a second dip of latex which contains a resorcinol/formaldehyde resin and cured again (e.g. the second coating on the cord is cured). In the single dip system, the adhesive coating is typically applied to a yarn (e.g. polyester yarn) during the drawing of the yarn or after a drawing of the yarn in a separate operation. The yarn is plied, or twisted, to form cords thereof which are treated with a latex which contains a resorcinol/formaldehyde resin and cured (e.g. the coating on the cord is cured). The need for the aforesaid diisocyanate dip in cord processing is not used by such single dip system.
U.S. Pat. No. 4,356,219 relates to use of an adhesive dip for reinforcing fabrics which contains an antidegradant. U.S. Pat. No. 4,472,463 relates to use of a second dip for coating cord or fabric made of polyester, where the dip is an aqueous emulsion containing an adhesive latex of a diene polymer and an acrylic resin. U.S. Pat. No. 3,749,758 relates to compositions containing polyesters and polyepoxides. U.S. Pat. No. 3,301,804 relates to tire yarns treated with an aqueous emulsion of an epoxy novalac and amino boron catalyst. U.S. Pat. No. 2,128,635 relates to application to a fabric of polyhydric phenol-aldehyde condensation products and latices. Blends of vinylpyridine/diene hydrocarbon resins, with rubber latices, have been suggested in U.S. Pat. No. Re. 23,451 for use for nylon cord.
The weaving, dipping, heat setting, and calendering of treated cord reinforcement for rubber compositions is explained in the Kirk Othmer Encyclopedia of Chemical Technology, end ed., Volume 20, Page 334, which is incorporated herein by reference into this specification. It is seen that adhesive formulations are only one part of the complex technology of fabric (cord) processing.
For example, latex based resorcinol-formaldehyde resin compositions for adhering various cords to rubber have been used for many years. They are the subject of many patent publications which involve, for example, variations in latices, variations in resin compositions and various additives to aid, for example, in resisting degradation to heat, to enhance stronger bonds and other beneficial effects.
Resins components as polyhydroxy and dihydroxy phenols have been reported for use in a dip at least as early as the aforesaid U.S. Pat. No. 2,128,635 for use in bonding cords (fabric) to rubber.
Blends of vinylpyridine/diene hydrocarbon latices with polyhydric phenol-aldehyde converted resols have been described, for example in the aforesaid U.S. Pat. No. Re. 23,451 which relates to adhesives for use with nylon cord.
An improvement on vinylpyridine/diene type adhesives is addressed in U.S. Pat. No. 3,194,294.
Use of polyhydric phenolic resins are also addressed, for example, in U.S. Pat. No. 3,437,122 and Canadian patent No. 984,076.
See also U.S. Pat. Nos. 4,572,863, 4,132,693 and 4,031,288.
Starch, particularly starch/plasticizer composites, have been suggested for use in elastomer formulations for various purposes, including for various tire components. For example see U.S. Pat. Nos. 5,969,211 and 5,672,639 which are incorporated by reference herein in their entirety.
For this invention, a pre-formed composite comprised of starch and water insoluble plasticizer therefor is contemplated to enable such plasticizer to have a plasticizing effect on the starch in order to reduce the softening point of the starch. For the purposes of this invention, water insoluble insofar as the plasticizer for the starch composite is concerned means a material which is not readily water soluble absent a significant increase in temperature or absent the presence of a material, other than the starch, which will render the plasticizer material soluble in water.
In the description of this invention, the term “phr” where used herein, and according to conventional practice, refers to “parts of a respective material per 100 parts by weight of rubber, or elastomer”.
In the description of this invention, the terms “rubber” and “elastomer” if used herein, may be used interchangeably, unless otherwise prescribed. The terms “rubber composition”,“compounded rubber” and “rubber compound”,if used herein, are used interchangeably to refer to “rubber which has been blended or mixed with various ingredients and materials” and such terms are well known to those having skill in the rubber mixing or rubber compounding art.